[Koha] how to create a library

HI! I'v installed koha! It's running perfect! Everything that i want is create a simple library but i don't know how do it. I'm trying but i'm confuse about catologues and biblios and Acquisitions and etc.. I want a simple library to a medium school. Someone could help me with a step by step or something like that? A hint at least.. really thank you!